U.S. patent number 7,477,913 [Application Number 11/097,145] was granted by the patent office on 2009-01-13 for determining a target transmit power of a wireless transmission according to security requirements.
This patent grant is currently assigned to Research In Motion Limited. Invention is credited to Neil Adams, Michael K. Brown, Michael S. Brown, Herb Little, Scott Totzke.
United States Patent |
7,477,913 |
Brown , et al. |
January 13, 2009 |
Determining a target transmit power of a wireless transmission
according to security requirements
Abstract
Different target transmit powers are determined for different
wireless transmissions from a wireless device, the different
transmissions having different security requirements. For example,
the security requirements of a particular transmission may include
a security ranking of a device to which one or more frames carried
by the particular transmission are addressed. In another example,
the security requirements of a particular transmission may include
the confidentiality of data carried by the particular
transmission.
Inventors: |
Brown; Michael K. (Kitchener,
CA), Totzke; Scott (Waterloo, CA), Little;
Herb (Waterloo, CA), Adams; Neil (Waterloo,
CA), Brown; Michael S. (Waterloo, CA) |
Assignee: |
Research In Motion Limited
(Waterloo, Ontario, CA)
|
Family
ID: |
37071260 |
Appl.
No.: |
11/097,145 |
Filed: |
April 4, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060223566 A1 |
Oct 5, 2006 |
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Current U.S.
Class: |
455/522; 380/270;
380/273; 455/69 |
Current CPC
Class: |
H04W
52/281 (20130101); H04L 63/20 (20130101) |
Current International
Class: |
H04M
11/00 (20060101) |
Field of
Search: |
;455/41.2,522,67.11 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Gareth Barlow, "Bluetooth Security", "Network and Inter-network
Security Report", Apr. 20, 2001, Cape Town, South Africa (see
www.cs.uct.ac.za/courses/CS400W/NIS04/papers2001/gareth.sub.--barlow.html-
). cited by other.
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Primary Examiner: Anderson; Matthew D
Assistant Examiner: Nguyen; Hai V
Attorney, Agent or Firm: Integral Intellectual Property Inc.
Paton; Miriam
Claims
What is claimed is:
1. A device comprising: a processor; a memory to store executable
code which, when executed by said processor, determines a target
transmit power for a wireless transmission based, at least in part,
on a security ranking of a device to which one or more frames
carried by said wireless transmission are addressed; and a wireless
transmitter to transmit said wireless transmission.
2. The device of claim 1, wherein said target transmit power is
lower for a wireless transmission carrying one or more frames
addressed to a device having a higher security ranking than for a
wireless transmission carrying one or more frames addressed to a
device having a lower security ranking.
3. The device of claim 1, wherein said device is a mobile
device.
4. The device of claim 1, wherein said device includes smart card
reader functionality.
5. The device of claim 1, wherein said device is a headset.
6. The device of claim 1, wherein said wireless transmitter is
compatible with a Bluetooth standard.
7. A device comprising: a processor; a memory to store executable
code which, when executed by said processor, determines a target
transmit power for a wireless transmission the based, at least in
part, on confidentiality of encrypted data carried by said wireless
transmission; and a wireless transmitter to transmit said wireless
transmission.
8. The device of claim 7, wherein said target transmit power is
lower for a wireless transmission carrying encrypted data of higher
confidentiality than for a wireless transmission carrying encrypted
data of lower confidentiality.
9. The device of 7, wherein said device is a mobile device.
10. The device of claim 7, wherein said device includes smart card
reader functionality.
11. The device of claim 7, wherein said device is a headset.
12. The device of claim 7, wherein said wireless transmitter is
compatible with a Bluetooth standard.
13. A device comprising: a processor; a memory to store executable
code which, when executed by said processor, determines different
target transmit powers for different wireless transmissions having
different security requirements; a wireless transmitter to transmit
said different wireless transmissions; and a wireless receiver,
wherein said executable code, when executed by said processor,
increases a target transmit power for a particular wireless
transmission in the absence of receipt of a valid response by said
wireless receiver from a device for which said particular wireless
transmission is intended.
14. The device of claim 13, wherein said device is a mobile
device.
15. The device of claim 13, wherein said device includes smart card
reader functionality.
16. The device of claim 13, wherein said device is a headset.
17. The device of claim 13, wherein said wireless transmitter is
compatible with a Bluetooth standard.
18. A method in a wireless-enabled device, the method comprising:
determining a target transmit power of a wireless transmission
based, at least in part, on a security ranking of a device to which
one or more frames carried by said wireless transmission are
addressed; and transmitting said wireless transmission.
19. The method of claim 18, wherein determining said target
transmit power of said wireless transmission includes determining a
lower target transmit power for a wireless transmission carrying
one or more frames addressed to a device having a higher security
ranking than for a wireless transmission carrying one or more
frames addressed to a device having a lower security ranking.
20. A method in a wireless-enabled device, the method comprising:
determining a target transmit power of a wireless transmission
based, at least in part, on confidentiality of encrypted data
carried by said wireless transmission; and transmitting said
wireless transmission.
21. The method of claim 20, wherein determining said target
transmit power of said wireless transmission includes determining a
lower target transmit power for a wireless transmission carrying
encrypted data of higher confidentiality than for a wireless
transmission carrying encrypted data of lower confidentiality.
22. A method in a wireless-enabled device, the method comprising:
determining different target transmit powers for different wireless
transmissions having different security requirements; transmitting
said different wireless transmissions; and increasing a target
transmit power of a particular wireless transmission in the absence
of a valid response from a device for which said particular
wireless transmission is intended.
Description
BACKGROUND OF THE INVENTION
In general, wireless communication is insecure and vulnerable to
attacks. Various techniques may be employed to secure a wireless
communication link or to make it less vulnerable to attacks. For
example, it is recommended to place a wireless access point away
from external walls and to lower the transmit power of its antenna
so that the signal strength is strong enough for use inside the
building but weak outside of the building where it may be
accessible by others.
Bluetooth.RTM. wireless technology provides short-range and low
power wireless connectivity to eliminate the need for cables to
connect computerized devices and their peripheral devices. A
non-exhaustive list of examples of computerized devices includes
personal computers (PCs), mobile phones, personal digital
assistants (PDA), portable computers, pagers, handheld devices, and
the like. A non-exhaustive list of examples of peripheral devices
includes headsets, printers, keyboards, mice, and the like.
The Bluetooth.RTM. specifications were designed with various
concepts in mind, including output power control that optimizes
power according to device distance. According to the Bluetooth.RTM.
specification version 1.2, there are three classes of transmitters,
and power control is mandatory only for those transmitters in the
class where the maximum output power is 100 mW (20 dBm) and the
minimum output power at the maximum power setting is 1 mW. At page
33 of the Radio Specification section of the Bluetooth.RTM.
specification version 1.2, it is stated "The power control (of a
power class 1 device) is used for limiting the transmitted power
over +4 dBm. Power control capability under +4 dBm is optional and
could be used for optimizing the power consumption and overall
interference level".
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention are illustrated by way of example and
not limitation in the figures of the accompanying drawings, in
which like reference numerals indicate corresponding, analogous or
similar elements, and in which:
FIG. 1 is a schematic diagram of an exemplary system, according to
some embodiments of the invention;
FIG. 2 is a flowchart of a method to be implemented by one of the
devices in FIG. 1, according to some embodiments of the invention;
and.
FIG. 3 is a block diagram of one of the devices in the system of
FIG. 1, according to some embodiments of the invention.
It will be appreciated that for simplicity and clarity of
illustration, elements shown in the figures have not necessarily
been drawn to scale. For example, the dimensions of some of the
elements may be exaggerated relative to other elements for
clarity.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
In the following detailed description, numerous specific details
are set forth in order to provide a thorough understanding of
embodiments of the invention. However it will be understood by
those of ordinary skill in the art that the embodiments of the
invention may be practiced without these specific details. In other
instances, well-known methods, procedures, components and circuits
have not been described in detail so as not to obscure the
embodiments of the invention.
FIG. 1 is a schematic diagram of an exemplary system, according to
some embodiments of the invention. A system 100 includes a mobile
device 102 and one or more additional devices able to communicate
with mobile device 102. For example, these other devices may
include peripherals such as a wireless smart card reader 104, a
wireless headset 106, and a wireless printer 108, which may be able
to communicate with device 102 over wireless communication links
114, 116 and 118, respectively. A non-exhaustive list of examples
of wireless local area network standards for wireless communication
links 114, 116 and 118 includes the Institute of Electrical and
Electronic Engineers (IEEE) for Wireless LAN MAC and Physical layer
(PHY) 802.11a, b, g and n specifications or future related
standards, the Bluetooth.RTM. standard, the Zigbee.TM. standard and
the like.
A smart card 103 is shown inserted into smart card reader 104.
Smart cards are personalized security devices, defined by the
ISO7816 standard and its derivatives, as published by the
International Organization for Standardization. A smart card may
have a form factor of a credit card and may include a semiconductor
device. The semiconductor device may include a memory that can be
programmed with a secret key and with an authentication
certificate, and may include a decryption engine, e.g., a processor
and/or dedicated decryption logic. A smart card may include a
connector for powering the semiconductor device and performing
serial communication with an external device. Alternatively, smart
card functionality may be embedded in a device having a different
form factor and different communication protocol, for example a
Universal Serial Bus (USB) device. The person whose security
information is stored on smart card 103 may use smart card reader
104 for identification and to digitally sign and/or decrypt
messages sent by device 102.
For example, mobile device 102 may be able to send and receive
e-mail messages via an e-mail server (not shown). If, for example,
the Secure Multipurpose Internet Mail Extensions (S/MIME) protocol
is used, e-mail messages received at mobile device 102 are
encrypted using a symmetric algorithm with a random session key
generated by the sender of the e-mail message. The e-mail message
also includes the session key, encrypted using the public key of
the recipient. Upon receipt of an encrypted e-mail message, mobile
device 102 may extract the encrypted session key and send it to
smart card reader 104 via communication link 114. Smart card reader
104 may send the encrypted session key to smart card 103, and the
decryption engine of smart card 103 may decrypt the encrypted
session key using the recipient's private decryption key, which is
stored in smart card 103. Smart card reader 104 may retrieve the
decrypted session key from smart card 103 and forward it to mobile
device 102 via communication link 114 so that mobile device 102 can
decrypt the received e-mail message. The smart card 103 may prevent
unauthorized use of the recipient's private decryption key by
requiring that a password or personal identification number (PIN)
be supplied before allowing the decryption operation to
proceed.
Similarly, to add a digital signature to an e-mail message being
sent by mobile device 102, mobile device 102 may send a hash of the
contents of the e-mail message to smart card reader 104 over
communication link 114. Smart card reader 104 may pass the hash to
smart card 103, which may produce a digital signature from the hash
and the sender's private signing key, which is stored in smart card
103. Smart card 103 may then pass the digital signature to smart
card reader 104, which may forward it to mobile device 102 via
communication link 114 so that mobile device 102 can transmit it
along with the e-mail message to the e-mail server. Again, smart
card 103 may prevent unauthorized use of the recipient's private
signing key by requiring that a password or PIN be supplied before
allowing the signing operation to proceed.
The unencrypted session key should be sent securely over
communication link 114 from smart card reader 104 to mobile device
102 to prevent a third party from retrieving the session key from
communication link 114. Similarly, the hash to be signed should be
sent authentically over communication link 114 from smart card
reader 104 to mobile device 102 to prevent a third party from
modifying the hash and thereby causing smart card 103 to produce a
signature using a hash different from the hash of the intended
message. Smart card reader 104 and mobile device 102 may each store
a common, symmetric key and use a symmetric algorithm to secure
communications over communication link 114. Alternatively, smart
card reader 104 and mobile device 102 may store their own private
keys and each other's public keys, and use an asymmetric algorithm
to secure communications over communication link 114.
Headset 106 may communicate with mobile device 102 over wireless
communication link 116 and may extend audio functionality of mobile
device 102. For example, mobile device 102 may include cellphone
functionality, and headset 106 may provide mobile device 102 with
audio input and output functions, enabling a user to listen to
voice mail, handle voice calls and issue voice commands to mobile
device 102. In another example, mobile device 102 may include audio
playback functionality, for example an MP3 (moving picture experts
group layer 3 audio) playback functionality, and headset 106 may
provide device 102 with an audio output function, enabling a user
to listen to audio playback.
Mobile device 102 may include data functionality, for example,
e-mail functionality. Mobile device 102 may be able to send data
over wireless communication link 118 to be printed by wireless
printer 108.
Wireless communication links 114, 116 and 118 may be vulnerable to
eavesdropping. However, mobile device 102 may be close physically
to one or more of devices 104, 106 and even 108. Thus, device 102
may be able to communicate with devices that are nearby at lower
powers than with devices that are farther away.
FIG. 2 is a flowchart of a method to be implemented by one or more
of devices 102, 104 and 106, according to some embodiments of the
invention. At 202, one or more of devices 102, 104 and 106 may
determine different target transmit powers for different wireless
transmissions having different security requirements. The stricter
the security requirements, the lower the target transmit power, so
that sensitive transmissions are "whispered" and therefore less
vulnerable to eavesdropping. The actual transmit power of a
wireless transmission, measured at the antenna of the transmitting
device, may differ from the target transmit power due to various
factors.
The security requirements of a particular transmission may include
a predetermined or dynamically determined security ranking of the
device to which one or more frames carried by the particular
transmission are addressed, with a lower target transmit power for
transmissions carrying frames addressed to devices at higher
security rankings than for transmission carrying frames addressed
to devices at lower security rankings.
For example, since communications between mobile device 102 and
smart card reader 104 may be generally more confidential than
communications between mobile device 102 and headset 106, mobile
device 102 may determine a lower target transmit power for
transmissions intended for smart card reader 104 than for
transmissions intended for headset 106. However, the security
ranking of a device may be dependent on other factors. For example,
the security ranking of smart card reader 104 may be lower while
the user is at an authorized workplace than while the user is
located outside the authorized workplace. At the authorized
workplace, mobile device 102 may determine a relatively high target
transmit power for transmissions intended for smart card reader 104
so as to avoid retries due to lack of reception by smart card
reader 104 of those transmissions.
In another example, if the sender of a transmission recognizes that
there are other transmitters in the area (for example, other active
Bluetooth.RTM. radios), the sender may reduce the target transmit
power of the transmission to make it harder for the other
transmitters to receive the transmission. This is analogous to
"whispering" when someone is standing nearby.
The security requirements of a particular transmission may include
the confidentiality of data carried by the particular transmission,
with lower target transmit powers for transmissions carrying data
of higher confidentiality than for transmissions carrying data of
lower confidentiality.
For example, telephone calls with members of the user's family may
be considered less confidential than telephone calls with the
user's co-workers. Accordingly, the target transmission power for
transmissions between mobile device 102 and headset 106 may be
lower for some telephone calls than for others.
In another example, documents may have different confidentiality
rankings. The target transmission power for transmitting documents
from mobile device 102 to printer 108 may vary according to the
confidentiality ranking of the document.
In yet another example, as explained hereinabove, to add a digital
signature to an e-mail message being sent by mobile device 102,
mobile device 102 may send a hash of the contents of the e-mail
message to smart card reader 104. Smart card reader 104 may pass
the hash to smart card 103, which may produce a digital signature
from the hash and the sender's private signing key, which is stored
in smart card 103. Smart card 103 may prevent unauthorized use of
the recipient's private signing key by requiring that a password or
PIN be supplied before allowing the signing operation to proceed.
Since the password or PIN is more confidential than the hash of the
contents of the e-mail message, mobile device 102 may determine a
lower target transmit power for the transmission carrying the
password or PIN than for the transmission carrying the hash of the
contents of the e-mail message.
If mobile device 102 does not detect a valid response from the
device for which the transmission is intended (checked at 204),
mobile device 102 may act according to a security policy. For
example, at 206, mobile device 102 may prompt the user to bring
mobile device 102 and the device for which the transmission is
intended closer together. In another example, at 208, mobile device
102 may increase the target transmit power for transmissions
intended for that device, possibly subject to an upper limit.
FIG. 3 is a block diagram of a device 300, according to some
embodiments of the invention. Device 300 may be, for example,
mobile device 102, smart card reader 104, or headset 106. For
clarity, some components of device 300 are not shown in FIG. 3 and
are not described explicitly below.
Device 300 includes an antenna 302. A non-exhaustive list of
examples for antenna 302 includes a dipole antenna, a monopole
antenna, a multilayer ceramic antenna, a planar inverted-F antenna,
a loop antenna, a shot antenna, a dual antenna, an omnidirectional
antenna and any other suitable antenna.
Device 300 also includes a wireless transceiver 304 including a
radio 303 coupled to antenna 302. Wireless transceiver 304 includes
both transmitter and receiver functionality. A non-exhaustive list
of examples for standards with which wireless transceiver 304 may
be compatible includes 802.11a, b, g and n and future related
standards, the Bluetooth.RTM. standard, the Zigbee.TM. standard and
the like.
Device 300 also includes a processor 306 coupled to transceiver
304. Device 300 also includes a memory 308, which may be fixed in
or removable from device 300. Memory 308 may be coupled to
processor 306 or partly embedded in processor 306. Transceiver 304
and processor 306 may be part of the same integrated circuit or in
separate integrated circuits. Similarly, processor 306 and memory
308 may be part of the same integrated circuit or in separate
integrated circuits.
A non-exhaustive list of examples for processor 306 includes a
central processing unit (CPU), a digital signal processor (DSP), a
reduced instruction set computer (RISC), a complex instruction set
computer (CISC) and the like. Furthermore, processor 306 may be
part of an application specific integrated circuit (ASIC) or may be
a part of an application specific standard product (ASSP).
A non-exhaustive list of examples for memory 308 includes any
combination of the following:
a) semiconductor devices such as registers, latches, read only
memory (ROM), mask ROM, electrically erasable programmable read
only memory devices (EEPROM), flash memory devices, non-volatile
random access memory devices (NVRAM), synchronous dynamic random
access memory (SDRAM) devices, RAMBUS dynamic random access memory
(RDRAM) devices, double data rate (DDR) memory devices, static
random access memory (SRAM), universal serial bus (USB) removable
memory, and the like;
b) optical devices, such as compact disk read only memory (CD ROM),
and the like; and
c) magnetic devices, such as a hard disk, a floppy disk, a magnetic
tape, and the like.
Memory 308 may store executable code 310 which, when executed by
processor 306, determines different target transmit powers for
different transmissions to be transmitted by transceiver 306 and
having different security requirements.
Executable code 310, when executed by processor 306, may cause
device 300 to implement the method of FIG. 2.
While certain features of the invention have been illustrated and
described herein, many modifications, substitutions, changes, and
equivalents will now occur to those of ordinary skill in the art.
It is, therefore, to be understood that the appended claims are
intended to cover all such modifications and changes as fall within
the spirit of the invention.
* * * * *
References